Vehicle location accuracy

1. A system comprising: a satellite-based positioning-system module configured to provide satellite-positioning data; a compass configured to provide compass data; a stability control system configured to provide stability control data; and a controller configured to maintain a last-known vehicle location, maintain, between vehicle key-on cycles, a satellite-positioning availability flag indicative of whether the satellite-positioning data is unavailable, and, when the satellite-positioning data is unavailable from the satellite-based positioning-system module, utilize the compass data and the stability control data to estimate a current vehicle location from the last-known vehicle location.

2. The system of claim 1 , wherein the controller is further configured to avoid use of the compass data to estimate the current vehicle location when the vehicle is accelerating or decelerating in East or West headings.

3. A system comprising: a satellite-based positioning-system module configured to provide satellite-positioning data; a compass configured to provide compass data; a stability control system configured to provide stability control data; and a controller configured to maintain a last-known vehicle location, and, when the satellite-positioning data is unavailable from the satellite-based positioning-system module, utilize the compass data and the stability control data to estimate a current vehicle location from the last-known vehicle location; wherein the controller is further configured to identify headings that are within a predetermined number of degrees from due East or West as being East or West headings.

4. The vehicle of claim 3 , wherein the predetermined number of degrees is +/−45 degrees.

5. The system of claim 1 , wherein the controller is further configured to: estimate the current vehicle location using a heading determined according to steering sensor data when the steering sensor data is available; and estimate the current vehicle location using a heading determined according to a previous heading when the steering sensor data is unavailable.

6. A computer-implemented method comprising: when satellite-based positioning-system data is available from a satellite-positioning module, identifying a current vehicle location via the satellite-positioning module; when satellite-based positioning-system data is unavailable, determining the current vehicle location based on a last-known vehicle location, compass heading from a compass, and stability control data from a stability control system, such that the compass heading is corrected according to forward acceleration and grade identified from the stability control data; and updating the last-known vehicle location according to the current vehicle location.

7. The method of claim 6 , further comprising: utilizing longitudinal accelerometer data and differential wheel speed to determine the grade; calculating forward distance traveled according to the grade; and outputting an indication of current vehicle location according to the forward distance traveled.

8. The method of claim 6 , further comprising estimating the current vehicle location in part according to a heading determined using steering sensor data.

9. The method of claim 6 , further comprising maintaining, between vehicle key-on cycles, a satellite-positioning availability flag indicative of whether the satellite-based positioning system data from the satellite-positioning module is unavailable.

10. A vehicle comprising: a controller configured to compute a plurality of estimates of a current location of the vehicle, each estimate being performed using a different non-satellite-based-positioning-system approach, one estimate based on vehicle-captured image data; identify a subset of the plurality of estimates of the current locations based on consistency relative to one another; and average the subset of the plurality of estimates to compute an overall current location of the vehicle.

11. The vehicle of claim 10 , wherein the controller is further configured to determine one of the plurality of estimates of the current location based on a last-known vehicle location, compass heading from a compass, and stability control data from a stability control system, such that the compass heading is corrected according to forward acceleration and grade identified from the stability control data.

12. The vehicle of claim 10 , wherein the controller is further configured to determine one of the plurality of estimates of the current location based on a previous vehicle heading and distance measure determined from wheel sensor data.

13. The vehicle of claim 10 , wherein the controller is further configured to avoid use of compass data to estimate the current location when the vehicle is accelerating or decelerating in East or West headings.

14. The vehicle of claim 13 , wherein the controller is further configured to identify headings that are within a predetermined number of degrees from due East or West as being East or West headings.

15. The vehicle of claim 14 , wherein the predetermined number of degrees is +/−45 degrees.

16. The vehicle of claim 10 , wherein the controller is further configured to determine one of the plurality of estimates of the current location by estimating the current location using a heading determined according to steering sensor data when the steering sensor data is available; and estimating the current location using a heading determined according to a previous heading when the steering sensor data is unavailable.